1. Field of the Invention
This invention relates to displays, more particularly to displays that must support multiple video standards and use two dimensional spatial light modulators (SLMs) as their light modulating elements.
2. Background of the Invention
From the 1950s through the early 1990s several video display standards have evolved. As display technology moves to high-definition displays (HDD) and high-definition television (HDTV), many more standardized formats have appeared. Some of these are ATV (Advanced Television) or US-HD (United States High Definition), possibly HD-MAC (High Definition Multiplexed Analogue Component), and MUSE (Multiple Sub-Nyquist-Sampling Encoding) in Japan. These formats all produce what are considered to be high-definition displays, yet all have different numbers of horizontal lines and different numbers of resolution elements (or pixels) along those lines, as well as different frame rates. All of the aforementioned HD formats except US-HD are analog, but the US format will be digitally implemented and specified, as are any number of computer display formats. The ability to present these numerous digital and analog standards adequately on a single display system in a cost effective manner can be an important performance and cost differentiator between competing display systems.
Sequentially scanned displays, like CRTs, can display pixels continuously through a scan line, limited only by the MTF of the monitor. Discrete sample displays, like those based on liquid-crystal devices (LCD) or digital micromirror devices (DMD) SLMs, have fixed pixel placements and aspect ratios that demand adjustment of the input data so incoming images with different aspect ratios, scales, and horizontal resolutions are displayed with acceptable fidelity. In these devices a picture is displayed on an array of rows and columns of individual cells. The analog standards must be sampled in these systems and pre- sampled digital standards may be sampled at resolutions incommensurate with the SLM resolution.
A problem then exists in building a display system that is portable among the analog standards, and yet still compatible with digital standards such as US-HD. If the system is built to be US-HD compatible, the problem of adjusting to the various analog standards exists. Since the number of samples and the aspect ratios and pitch of the pixels will not be an exact match for any of the other standards, resampling or scaling of the data will be required. Total display system complexity, including the image processing system as well as the SLM system, will depend on the trade-offs between the SLM design and the processing algorithms. Within these trade-offs consideration must be given to problems of aliasing, poor picture quality and expense.